It is known in the art relating to engine crankcases that crankshaft support webs are required to absorb major stresses from the combustion and inertia loads developed in the engine cylinders and from the reciprocating and rotating masses connected to the crankshaft throws. To withstand these loads, engine crankcases and cylinder blocks may be formed as a single casting and machined with the crankshaft bearing caps in place. The bearing caps are then cracked off with a mandrel, leaving a generally horizontal split line of cracked surfaces at which the bearing caps are reattached to the crankcase with bolts or studs.
To minimize stresses, joining of the support webs to crankcase sidewalls makes use of smoothly curved joints avoiding sharp angles which would introduce stress risers. These joints begin above the split line for the bearing caps, which may limit the space available for larger stress reducing radii in the support webs themselves. Such a problem was presented when it was desired to increase the fatigue strength of an already completed crankcase design without changing the basic crankcase dimensions.